Spin valve thin-film magnetic device having free magnetic layer in ferrimagnetic state and manufacturing method therefor

Abstract

A spin valve thin-film magnetic device is provided, in which the asymmetry can be reduced. The spin valve thin-film magnetic device comprises a free magnetic layer and a first and a second fixed magnetic layer, which are provided respectively at each side of the free magnetic layer in the thickness direction thereof. In the spin valve thin-film magnetic device, the free magnetic layer is composed of a first and a second ferromagnetic free layer, in which the entire free magnetic layer is in a ferrimagnetic state, the first fixed magnetic layer is composed of a first and a second pinned ferromagnetic layer, in which the entire first fixed magnetic layer is in a ferrimagnetic state, and the second fixed magnetic layer is composed of a third and a fourth pinned ferromagnetic layer, in which the entire second fixed magnetic layer is in a ferrimagnetic state. In addition, magnetization directions of the second and the third pinned ferromagnetic layers, which are closer to the free magnetic layer, are antiparallel to each other.

What is claimed is:  
     
       1. A spin valve thin-film magnetic device comprising: 
       a free magnetic layer;  
       a pair of nonmagnetic conductive layers formed on both sides of the free magnetic layer in the thickness direction thereof;  
       a pair of fixed magnetic layers formed on the pair nonconductive layers;  
       a pair of antiferromagnetic layers formed on the pair of fixed magnetic layers;  
       a pair of conductive layers imparting a sensing current to the free magnetic layer, the pair of nonmagnetic conductive layers, and the pair of fixed magnetic layers; and  
       a pair of bias layers for aligning a magnetization direction of the free magnetic layer;  
       wherein the free magnetic layer is a laminate composed of at least 2L ferromagnetic layers with a nonmagnetic interlayer provided therebetween, the L being an integer of 1 or more, in which magnetization directions of the ferromagnetic layers adjacent to each other are antiparallel,  
       one of the pair of fixed magnetic layers is a laminate composed of at least 2M ferromagnetic layers with a nonmagnetic layer provided therebetween, the M being an integer of 1 or more, in which magnetization directions of the ferromagnetic layers adjacent to each other are antiparallel, and a second direction of a second magnetic moment of the entire fixed magnetic layer by an exchange coupling magnetic field formed by the one of the pair of fixed magnetic layers and the one of the pair of antiferromagnetic layers adjacent thereto, is fixed in a direction crossing a first direction of a first magnetic moment of the entire free magnetic layer,  
       the other fixed magnetic layer is a laminate composed of at least 2N ferromagnetic layers with a nonmagnetic layer provided therebetween, the N being an integer of 1 or more, in which magnetization directions of the ferromagnetic layers adjacent to each other are antiparallel, and a third direction of a third magnetic moment of the entire other fixed magnetic layer by an exchange coupling magnetic field formed by the other fixed magnetic layer and the other antiferromagnetic layer adjacent thereto, is fixed in a direction parallel to the second direction of the entire fixed magnetic layer, and  
       a magnetization direction of a ferromagnetic layer, which is closest to the free magnetic layer among the ferromagnetic layers forming the fixed magnetic layer, and a magnetization direction of a ferromagnetic layer, which is closest to the free magnetic layer among the ferromagnetic layers forming the other fixed magnetic layer, are antiparallel to each other.  
     
     
       2. A spin valve thin-film magnetic device according to  claim 1 , wherein the direction of a magnetic field moment Hb 1  of a ferromagnetic exchange coupling magnetic field formed by ferromagnetic interlayer coupling between the free magnetic layer and the ferromagnetic layer, which is closest to the free magnetic layer among the ferromagnetic layers forming the fixed magnetic layer, and the direction of a magnetic field moment Hb 2  of a ferromagnetic exchange coupling magnetic field formed by ferromagnetic interlayer coupling between the free magnetic layer and the ferromagnetic layer, which is closest to the free magnetic layer among the ferromagnetic layers forming the other fixed magnetic layer, are antiparallel to each other in the free magnetic layer. 
     
     
       3. A spin valve thin-film magnetic device according to  claim 1 , wherein the L is 1, the M is 1, and the N is 1. 
     
     
       4. A spin valve thin-film magnetic device according to  claim 1 , 
       wherein the fixed magnetic layer is a laminate composed of a first ferromagnetic layer and a second ferromagnetic layer with a first nonmagnetic layer provided therebetween, the thickness of the second ferromagnetic layer formed at a location closer to the free magnetic layer being larger than that of the first ferromagnetic layer, and  
       the other fixed magnetic layer is a laminate composed of a third ferromagnetic layer and a fourth ferromagnetic layer with a second nonmagnetic layer provided therebetween, the thickness of the third ferromagnetic layer formed at a location closer to the free magnetic layer being smaller than that of the fourth ferromagnetic layer.  
     
     
       5. A spin valve thin-film magnetic device according to  claim 1 , 
       wherein the fixed magnetic layer is a laminate composed of a first ferromagnetic layer and a second ferromagnetic layer with a first nonmagnetic layer provided therebetween, the thickness of the second ferromagnetic layer formed at a location closer to the free magnetic layer being smaller than that of the first ferromagnetic layer, and  
       the other fixed magnetic layer is a laminate composed of a third ferromagnetic layer and a fourth ferromagnetic layer with a second nonmagnetic layer provided therebetween, the thickness of the third ferromagnetic layer formed at a location closer to the free magnetic layer being larger than that of the fourth ferromagnetic layer.  
     
     
       6. A thin-film magnetic head for reading magnetically written information, comprising a spin valve thin-film magnetic device according to  claim 1 . 
     
     
       7. A floating type magnetic head comprising: 
       a slider; and  
       a thin-film magnetic head according to  claim 6  provided in the slider.  
     
     
       8. A spin valve thin-film magnetic device comprising: 
       a free magnetic layer;  
       a pair of nonmagnetic conductive layers formed on both sides of the free magnetic layer in the thickness direction thereof;  
       a pair of fixed magnetic layers formed on the pair of nonconductive layers;  
       a pair of antiferromagnetic layers formed on the pair of fixed magnetic layers;  
       a pair of conductive layers imparting a sensing current to the free magnetic layer, the pair of nonmagnetic conductive layers, and the pair of fixed magnetic layers; and  
       a pair of bias layers for aligning a magnetization direction of the free magnetic layer;  
       wherein the free magnetic layer is a laminate composed of at least 2L ferromagnetic layers with a nonmagnetic interlayer provided therebetween, the L being an integer of 1 or more, in which magnetization directions of the ferromagnetic layers adjacent to each other are antiparallel,  
       one of the pair of fixed magnetic layers is a laminate composed of at least 2M ferromagnetic layers with a nonmagnetic layer provided therebetween, the M being an integer of 1 or more, in which magnetization directions of the ferromagnetic layers adjacent to each other are antiparallel, and a second direction of a second magnetic moment of the entire fixed magnetic layer by an exchange coupling magnetic field formed by the one of the pair of fixed magnetic layers and the one of the pair of antiferromagnetic layers adjacent thereto, is fixed in a direction crossing a first direction of a first magnetic moment of the entire free magnetic layer,  
       the other fixed magnetic layer is one of a single ferromagnetic layer and a laminate composed of at least 2N+1 ferromagnetic layers with a nonmagnetic layer provided therebetween, the N being an integer of 1 or more, magnetization directions of the ferromagnetic layers adjacent to each other being antiparallel, and a third direction of a third magnetic moment of the entire other fixed magnetic layer by an exchange coupling magnetic field formed by the other fixed magnetic layer and the other antiferromagnetic layer adjacent thereto, is fixed in a direction antiparallel to the second direction of the entire fixed magnetic layer, and  
       a magnetization direction of a ferromagnetic layer, which is closest to the free magnetic layer among the ferromagnetic layers forming the fixed magnetic layer, and a magnetization direction of a ferromagnetic layer, which is closest to the free magnetic layer among the ferromagnetic layers forming the other fixed magnetic layer, are antiparallel to each other.  
     
     
       9. A spin valve thin-film magnetic device according to  claim 8 , wherein the direction of a magnetic field moment Hb 1  of a ferromagnetic exchange coupling magnetic field formed by ferromagnetic interlayer coupling between the free magnetic layer and the ferromagnetic layer, which is closest to the free magnetic layer among the ferromagnetic layers forming the fixed magnetic layer, and the direction of a magnetic field moment Hb 2  of a ferromagnetic exchange coupling magnetic field formed by ferromagnetic interlayer coupling between the free magnetic layer and the ferromagnetic layer, which is closest to the free magnetic layer among the ferromagnetic layers forming the other fixed magnetic layer, are antiparallel to each other in the free magnetic layer. 
     
     
       10. A spin valve thin-film magnetic device according to  claim 8 , wherein the direction of a magnetic moment Hd 1  of a dipole magnetic field of the fixed magnetic layer and the direction of a magnetic moment Hd 2  of a dipole magnetic field of the other fixed magnetic layer are antiparallel to each other in the free magnetic layer. 
     
     
       11. A spin valve thin-film magnetic device according to  claim 8 , wherein, when the sensing current flows in the pair of nonmagnetic conductive layers, a magnetic moment Hs of a sensing current magnetic field applied to the free magnetic layer is represented by the formula below, Hb 1 +Hb 2 +Hd 1 +Hd 2 +Hs≅0. 
     
     
       12. A spin valve thin-film magnetic device according to  claim 8 , wherein the L is 1, the M is 1, and the other fixed magnetic layer is a single ferromagnetic layer. 
     
     
       13. A spin valve thin-film magnetic device according to  claim 8 , wherein the L is 1, the M is 1, and the N is 1. 
     
     
       14. A spin valve thin-film magnetic device according to  claim 8 , wherein, when the sensing current flows, the direction of a sensing current magnetic field applied to the fixed magnetic layer and the magnetization direction of the entire fixed magnetic layer are in the same direction, and the direction of a sensing current magnetic field applied to the other fixed magnetic layer and the magnetization direction of the entire other fixed magnetic layer are in the same direction. 
     
     
       15. A thin-film magnetic head for reading magnetically written information, comprising a spin valve thin-film magnetic device according to  claim 8 . 
     
     
       16. A floating type magnetic head comprising: 
       a slider; and  
       a thin-film magnetic head according to  claim 15  provided in the slider.